This invention relates to a process for gasification of carbonaceous materials to produce a carbon monoxide-rich gas. More specifically, this invention relates to increasing the amount of carbon monoxide produced in a process of gasifying carbonaceous materials at elevated temperatures to maximize the yield of carbon monoxide from such a process.
Oil and natural gas are used as feedstocks or fuels for many chemical and mechanical processes. These raw materials are rapidly becoming depleted and alternative sources are being developed. One alternative source present in the United States is the vast deposits of coal. Coal, coal gasification, and coal liquefaction products are seriously being promoted as substitute feedstocks and fuels for chemical and mechanical processes.
Reducing and synthesis gases that are useful as fuels and as reactants in ore reduction processes have been produced by catalytic reforming of natural gas via the methane-steam reaction, partial oxidation of hydrocarbon fuels, and by gasification of coal and coke. Because of the depletion of oil and natural gas, more emphasis is being placed on the production of reducing and synthesis gases from coal and coke gasification. The production of a carbon monoxide-rich reducing gas by gasification of coal or coke has become of increasing interest. This carbon monoxide-rich reducing gas is useful since the carbon monoxide reacts with many metal oxides or other metallic compounds, such as metallic halides, to produce carbon dioxide and the corresponding metals or lower metal oxides. A few of the metals whose oxides are reduced by carbon monoxide include iron, aluminum, cobalt, copper, lead, manganese, molybdenum, nickel, silver and tin. In addition, a carbon monoxide-rich gas has many other chemical applications, such as the production of metal carbonyls, phosgene, toluene diisocyanate, and synthetic acids, including acetic acid. The carbon monoxide is also employed in oxo synthesis processes, and developments are reported to be underway to employ carbon monoxide for production of terephthalic acid and p-cresol, and to use it as a co-monomer in thermoplastics.
The production of carbon monoxide-containing reducing gas by coal or coke gasification has been performed for many years by blue gas generators and producers, water gas generators, blast furnaces and coke ovens. The gas produced by these methods contains carbon monoxide along with quantities of hydrogen, water, carbon dioxide, methane and hydrogen sulfide. A recent development has occurred in the art to increase the yield of carbon monoxide obtained from coal and coke gasification. This development involves pre-drying the coal to be gasified with air, oxygen, and/or steam while supplying carbon dioxide to the gasification reaction. Several examples where carbon dioxide addition to the gasifier is disclosed are in U.S. Pat. Nos. 3,801,288 (Leas et al.); 3,840,353 (Squires); and 3,976,442 (Paull et al.). According to these teachings, the carbon dioxide added to the gasifier can be produced internally in the gasification process or can be introduced from an external source. This method does increase the amount of carbon monoxide in the raw gas emitted from the gasifier but the presence of other gases, most notably hydrogen, cannot be avoided due to the natural consistency of coal as well as due to the thermo-dynamic constraints which govern gasifier performance.
It is an object of the present invention to provide a process for maximizing the production of a carbon monoxide-rich gas from a process for the gasification of carbonaceous materials.
It is a further object of the present invention to provide a gasification process to produce a carbon monoxide-rich gas in an efficient, safe, and economic manner utilizing available heat sources present in the process.
It is an additional object of the present invention to provide an integrated process gasification of carbonaceous material to supply a sufficient amount of carbon monoxide for an ore reduction process, and for utilizing carbon dioxide produced in the ore reduction process to produce more carbon monoxide in the process for gasification of carbonaceous materials.
It is another additional object of the present invention to provide a process whereby hydrogen present in gases produced by gasification processes for carbonaceous materials is utilized in the production of the increased amount of carbon monoxide from the gasification process.